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To get some practice in flame-oxidizing of bare copper and making glass-to-copper seals
. And because
a spider is less boring than bare beads-on-a-wire. And to have pretty gifts.
Stranded copper wire was cut to lengths for the legs and the eyes. The wires were twisted together
in quads, to model the side legs. Then they were briefly heated in a torch flame, to dark red heat, and let cool.
The wires became black with the copper(II) oxide layer.
Small glass beads were strung on the stranded wire and positioned where they should be. Then they were heated in a torch flame, to orange-red, and let melt and wet the wire. Prolonged heating led to lowering of the glass viscosity too much, and the bead turned into a drop. This was exploited with the ends of eyes and legs, where beads were positioned at the very ends of the wires and heated until they melted into round drops.
The twisted-together ends were inserted into large beads and heated until the beads melted and fused with the oxide-coated copper.
Eyes were made from another short piece of wire, with a center bead, a tube bead for each eye, and terminated with a small round bead. The assembly was fused to the copper.
The large beads of the left and right sides were placed together on a refractory brick and heated with a flame until they partially melted and fused. A large bead was added in between them and heated again, until it fused as well and formed the posterior. The eyes assembly was positioned from the other side and also heated and fused.
The individual joints and glass-metal interfaces were then inspected with a stereomicroscope and found more or less satisfying.
The large beads tend to be too cold for too long and let carbon from the flame deposit on their surfaces and then become fused into it. This may be considered a flaw or an interesting surface effect. As it is undesirable for technological use of glass-metal joining, methods for eliminating it will be investigated.
The copper oxide layer tends to flake off when the metal is bent. It also tends to grow thick with further heating and weaken the joint. Just-right thickness has to be achieved for a proper vacuum-tight feedthrough.
The first one.
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A smaller, blue spider with fused-glass bottom
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A yet smaller, green spider
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Similarly sized orange spider, Barbara
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The red glass tends to discolor when intensely heated. A subsequent heat treatment is required to bring the color back.
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